Builders,

Here is a look ahead at a new part which we will have on the shelf by the end of the month, and publicly show at Corvair College #43 in November. It is a modified and refined version of our traditional #4201 nose bowl, it is specifically aimed at High performance Corvairs like the 3.3L engine in STOL aircraft Like the Zenith 750, but it also has logical use on many Corvairs in very hot climates.

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Above, The orange part is the semi-finished plug for the STOL Bowl, which is now at my composite shop, being used to make a brand new set of molds. Professional tooling is expensive, but required for good production parts. These costs are only made back after one and a half or two years of selling finished parts. I’m not focused on profitability here, I want the the best item available to serve the engine. Below it is the nose bowl from my Vagabond, first flown in 2004, modified with the inlet rings in 2013. It is a one piece bowl, I have used them on many of our own planes, but all of our production bowls are 2 piece split designs. The bottom part is a production #4201 nose bowl. more than 170 of these are on flying planes, we have produced them since 2005. They have served on almost every flying Corvair powered Zenith you have seen. The basic shape and size of all three are identical, the are all derived from the same plug I made a decade and a half ago, only the inlets are different.

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Above: Here is what will be different about the STOL Bowl: The inlets have an interior diameter of 5-3/8″ and built in inlet rings 1-3/8″ deep. In the above photo they are not fully faired in, as the composite shop is doing that before making the tooling, but it gives a good idea of what the production parts will look like. My Wagabond cowl in the background was the focus of this how to story I wrote 5 years ago this month:CHT part #3, Letters, notes, sources and inlets., outlining how to put inlet rings in cowls and suggested diameters. The Wagabond Bowl has 5″ inlets , and anyone could have copied this with some care and effort.

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It has been frustrating to me that the majority of builders paid no attention to my stories of optimizing cooling. At the bottom of this article are links to stories of testing that took me 100’s of hours to accomplish, yet many people never bothered to read them.. They devoted years to building their plane and engine, months to wiring glass panels and painting, but couldn’t put a single afternoon into making the cooling system work. Plenty of them never cut out the inlets much past 3-3/4″ and were mystified why their planes ran hotter than others. Some of these people went on to ask internet discussion groups what the issue was, and were given implausible suggestions about scoop systems, when the answer was simply cutting out the hole in the cowl.

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By making the STOL Bowl inlets larger and building in the rings, I’m not only making a better high output Bowl, but also effectively making sure that new planes have inlet rings from the start. Although we have built many successful STOL installations based on the original cowl in the last 15 years: STOL and utility planes for Corvair power, it will be easier for builders to replicate moving forward.

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Quick Questions and Simple Answers:

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How soon?

My composite shop is confident that we will have tooling and the first 12 cowls from the tool by the end of October.

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Will all the existing baffling and Cowl sheet metal remain the same?

Yes, these will be 100% compatable with those items, and the STOL Bowl with be directly retrofittable to existing installations

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How much will it cost?

Unknown until the first round is made, but the agreed target between myself and the composite shop is no more than 20% over the current #4201 bowl. Right now I have 6 existing orders for bowls, and those builders will have their wait rewarded, and can have either Bowl they like at the existing price. All orders after 10/4/18 will have to pay the difference for the STOL Bowl.

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What if I have a #4201 already? Is there a break on up grades?

Yes, it is my intention to offer an exchange program. I’m even willing to develop a reasonable discount for people who have already cut, fit, drilled and worked with their #4201 Bowl. I have a long history of never screwing builders on upgrades to existing systems. There are costs, but I have never treated any upgrade as revenue from hostages. When I know the exact pricing, I will release the upgrade numbers also. As a favor to me, do not call the SPA office and ask about pricing yet. If it isn’t posted here yet, they don’t know it. We don’t want to make unrequired work for them just because I’m giving builders a heads up on a product.

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Above, the perfect example of a builder never cutting out the inlet on a plane. I took this at the 2018 Zenith open house where we were also holding Corvair College #42. The owner flew this plane in, and obviously never paid attention to my stories about about inlets or inlet rings. I was going to mention this to him, but he never spoke to either Dan nor Myself, even though the parked the plane 150′ from our tent and was there several hours, and then flew away. How do I offer assistance to this person? When his plane cools below its potential, everyone at his airport has an opinion, but none of them understand I can do everything to assist people, but some people are not listening. If people think I’m making up stories about this, I have at least a dozen other pictures just like this, of flying planes, some of them belonging to people who have publicly complained on the net about cooling.

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Above is a shot of Rick Lindstrom’s 601XL, outside our hangar in 2007. I have been writing stories about cooling for a long time, and producing examples that work. Do the inlets on the Bowl above look like the ones on Rick’s plane? They came from the exact same mold, but the builder above put no effort in to addressing the inlets. Rick’s aircraft has flown all over the US. It has been in FL, Southern California and to Washington state. It has been seen by builders at the Sun n Fun, Arlington and Copper State (AZ) airshows. It even won the best engine trophy. A number of pilots have flown it long distances Like Rick, Amy Choi, Woody Harris and Michael Heintz. It flew across the US in the middle of a heat wave that showed outside air temps above 105F at 9,500 feet. The plane was flying at a special gross of 1425 pounds for the flight. It was climbed under these conditions at wide open throttle for over 50 minutes without pause after a number of fuel stops. This climb was flown at airspeeds near 65 mph. Yet it never over heated nor detonated, period. It has the exact same cooling system that we teach builders to install on their Zeniths. Physics doesn’t play favorites. It works here, and if you build a copy of this, it will work on your plane. Let anyone who thinks we don’t know how to cool a Corvair explain the history of this aircraft….they can’t.

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Above is the nosebowl from our Zenith 601XL. We started flying this in 2004, and it has been pictured in many places on my website. Do these inlet look like the ones on the builders plane at the top? This part came off the same tool that made the builders Bowl, but I put another 2 hours into cutting the openings and putting in inlet rings. Look at old pictures from Oshkosh 2005. This bowl was on my plane when I was using a very special hot rod 190cid 11:1 compression engine, making about 125hp. We flew it to Oshkosh with the plane loaded with a weeks display, books and camping gear. Every take off was over 1,500 pounds and some of them were above 100F OAT, didn’t overheat at all. This very bowl was used for 600+ hours on Andy Elliot’s 601XL in Arizona, without heat issues. If builders will not cut the inlets and put in rings, the STOL Bowl will do it for them.

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Above, From the 2016 story:Corvair Thermal Image Testing , We had just finished a short run, and the video camera was still looking at the engine. There are always “internet experts” who want to critique my thoughts on cooling, but considering they don’t often use their full names, and have never done a test on a Corvair like the one above, perhaps they can just be written off as people unable to cope with their unfortunate childhood. When I say things, it reflects 5 years at the worlds greatest aviation university, 29 years of Corvair flight engine experience, countless tests like the one above, and the humility to listen to people who know more than I do, and the common sense to ignore those who know next to nothing.

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KEEP IN MIND: Paul’s 3,000cc Corvair isn’t a new engine, it has 240 hours on it. A new engine should never be run without a cowl or airbox even for 1 minute. Take my word for it, without a cowl, the temp comes up much faster than you would think. In the image it is very easy to see how cool the welded on intake pipes stay on the heads (because they have cool air and evaporating gas flowing through them) The camera can pick up temp differences down to 1 degree.

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Above, the same angle, repeated here so it comes up as the lead picture in FB links to this story. I will share more information as I have it. Thanks, William.

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More information: This blog has incredibly good tracking on it. It will not tell me exactly who looked at each story, but it does tell me exactly how many people read each story in a given 24 hour period. Typically, about 600 people read the website on an average day, somethimes twice that for a story like the JaG-2 twin. The 600 people read several stories on average, for an average total of 1,500-2,000 stories read per day. By tomorrow, I will be able to see exactly how many people read each of the links below. It would be nice if people bothered to read and learn from them, but the data will invariably show only 5-10% of the people who look at this story will read even one of the links. Not much I can do about this, the National trend is to scan information, not read it. Our national attention span has been plummeting since the first issue of USA Today was printed. If you want to improve your person understanding, read.